1. Field of the Invention
This invention relates generally to Emitter Locating Systems and, more specifically, to a Real-time Emitter Locating System and Method
2. Description of Related Art
Emitter Location (EL) Systems are used to locate the position of emitting radio transmitters. Presently in the industry today, finding the location of a radio transmitter involves triangulation methods using at least three radio Direction Finding (DF) “Sets”. Inherently though, the DF Sets that comprise EL Systems produce uncertainties in their measurements due to several factors which will be described later. The invention of this disclosure provides a far more accurate method of operating EL Systems than is presently done today.
As mentioned, present day EL Systems are comprised of multiple radio Direction Finding (DF) Sets which can either be fixed in location, or mobile on a vehicle, ship, aircraft, etc. The invention of this disclosure especially relates to EL Systems employing at least one mobile DF Set. In fact, with the use of the technique and method of this patent, only a single mobile DF Set is required in an EL System. To understand how uncertainties in the DF Set measurements are reduced with this invention, the background of direction finding operations needs to covered.
The basic components of a DF Set are: (1) a DF antenna array; and (2) a DF receiver/processor (hereafter referred to simply as “DF receiver”). The basic components of an EL System are: (1) at least one DF Set; (2) some device to interpret the streaming Line-Of-Bearing (LOB) data sets from the DF Set; (3) some sensor device to determine the DF Set's location; and (4) some sensor device to output the DF Set's orientation relative to true North.
The major sources of measurement errors in real-world DF Sets are: (1) uncertainties from the DF antenna array due to frequency dependent variations; and (2) received signal reflections (also known as multi-path).
Typically in a DF Set, a device is attached to the output that collects, interprets, and plots the line-of-bearing (LOB) data. This device is typically a computer which then displays the LOB's on some sort of map display. The LOBs that are displayed will vary from measurement to measurement depending on the aforementioned uncertainties. Most often in the industry today though, the DF Sets simply take the collected LOB data sets and average them to produce a best guess as to the true LOB to the transmitter. But as mentioned, the resulting LOB invariably has some level of error, which translates to errors in overall determination of the transmitter's location.
Another problem with present-day DF Sets is that the calculation of the transmitter's location is done by a batch process. That is, the output is calculated by taking every single previous measurement and doing an analysis on the entire aggregate set of data. This is a slow process and cannot be done in real time with large sets of data.
The invention described in this disclosure uses an improved method and technique to collect data from one or multiple DF Sets, and then to intelligently process that data in real time so that overall measurement uncertainties are reduced. Thus the transmitter's position plotted on a map will be more accurate. It should be reiterated that with the method and technique of this invention, it is possible to determine, and continuously plot on a map, the location of a transmitter by using only a single DF Set. This fact makes this invention further unique.
In conclusion, insofar as the inventor is aware, no invention formerly developed provides this unique application of methods to significantly reduce EL system measurement uncertainties.